Yup yup, found that one and have read it probably 5 times now due to my anxiety It looks pretty similar to that, and I was content for about a day thinking that's all it was. It's just kind of suspicious to me that it happened during the mini-cycle too It also happened in less than a 48 hour period...is that possible for marbling?

Yeah I could see where you would be questioning it. I've had marbles before they never did any thing that crazy like in the article, but I have had them change over night. I would say that if he isn't acting lethargic, eating well, and your water parameters are fine then just keep an eye on him. My guess from the pictures you have posted would be that he is marbling.

I noticed some fin rot that was showing up since yesterday getting worse, so I QT'd Cobalt in my gallon tank with 1 tsp of AQ salt. The thing that tipped me off was the hole that developed in his upper fin. When I first got him, I made the newbie mistake of a fish in cycle, during which I noticed the same finrot hole. Currently, I believe the fin rot is most definitely related to the re-cycling going on and the spikes in Ammonia. I never saw the pink coloration before, so that might just be marbling. I swear, if his genes decided to marble at the same time as the cycle that would be one stressful coincidence (mostly for me)!

Thought I'd post an update. End of the second day of QT, he's acting very in character (begs for food, runs from camera). The minor fin rot seems to have stopped its advance, so hopefully he should be showing some healing soon. Treating with 1 tsp AQ salt/gallon with the full water change each day. Here's the two pictures I managed to get through my sneaky methods (setting up a webcamera next to the tank and catching him sleeping in range

The pink coloration has spread to about half of the body, and the white coloration on his neck and head has become more pronounced. I don't seem to see any fuzz on the scales, except that one patch is kind of shiny on his right side. He's eating well, and I just ordered some bloodworms that should get here next week

That coloration is not normal... He is not changing colors he has something. The reason I point that out, is because the color is a dull color with a grey undertone. What meds do you have on hand and what can you get ASAP?

That coloration is not normal... He is not changing colors he has something. The reason I point that out, is because the color is a dull color with a grey undertone. What meds do you have on hand and what can you get ASAP?

The Fungus clear has a chance. My personal first choice is Kanaplex and second Maracyn Plus

I've been treating him with Aquarium Salt since he was showing signs of some fin rot. Can you do epsom at the same time? If you think that would help I could make a trip tomorrow to get some since I don't have any. I'm really wary of exposing him to medicine unless I'm sure it will help...